Tab Layout

使用tab layout时，必须用tabHost和TabWidget，根节点必须是TabHost；包含一个布局，TabWidget（显示tab），FrameLayout(显示内容),点击tab切换不同的内容，有两种不同的方式。

第一种是没一个tab对应一个activity，第二种是，所有的tab都在一个activity中使用。

代码都是从文档上复制而来：下面展示的第一种，第一种更灵活，订制更复杂的信息

main.xml

<?xml version="1.0" encoding="utf-8"?>
<TabHost xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@android:id/tabhost"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
    <LinearLayout
        android:orientation="vertical"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:padding="5dp">
        <!--  tab 显示 -->
        <TabWidget
            android:id="@android:id/tabs"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content" />
         <!--  内容 -->   
        <FrameLayout
            android:id="@android:id/tabcontent"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:padding="5dp" />
    </LinearLayout>
</TabHost>

activity

  public class TabWidgetActivity extends TabActivity {

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
    	super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		Resources res = getResources(); // Resource object to get 
		TabHost tabHost = getTabHost(); // The activity TabHost
		TabHost.TabSpec spec; //  TabSpec for each tab
		Intent intent; // Reusable Intent for each tab
		// Create an Intent to launch an Activity for the tab (to be reused)
		intent = new Intent().setClass(this, ArtistsActivity.class);
		//新建一个TabSpec  tabHost.newTabSpec(tag名).setIndicator(CharSequence label, 显示的activity xml文件).setContent(设置到intent);
		spec = tabHost.newTabSpec("artists").setIndicator("Artists", res.getDrawable(R.drawable.ic_tab_artists)).setContent(intent);
		tabHost.addTab(spec);//添加到TabHost
		// Do the same for the other tabs
		intent = new Intent().setClass(this, AlbumsActivity.class);
		
		spec = tabHost.newTabSpec("albums").setIndicator("Albums", res.getDrawable(R.drawable.ic_tab_albums)).setContent(intent);
		tabHost.addTab(spec);

		intent = new Intent().setClass(this, SongsActivity.class);
		spec = tabHost.newTabSpec("songs").setIndicator("Songs", res.getDrawable(R.drawable.ic_tab_songs)).setContent(intent);
		tabHost.addTab(spec);

		tabHost.setCurrentTab(2);//当前显示哪个tab
       }
    }

   在res文件夹下新建一个drawable，下有三个activty的layout布局文件

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <!-- When selected, use grey 图片-->
    <item android:drawable="@drawable/ic_tab_artists_grey"
          android:state_selected="true" />
    <!-- When not selected, use white 图片 -->
    <item android:drawable="@drawable/ic_tab_artists_white" />
</selector>

  关于selector标签的用法：

<selector xmlns:android="http://schemas.android.com/apk/res/android"
    android:constantSize=["true" | "false"]
    android:dither=["true" | "false"]
    android:variablePadding=["true" | "false"] >
    <item
        android:drawable="@[package:]drawable/drawable_resource"
        android:state_pressed=["true" | "false"]
        android:state_focused=["true" | "false"]
        android:state_hovered=["true" | "false"]
        android:state_selected=["true" | "false"]
        android:state_checkable=["true" | "false"]
        android:state_checked=["true" | "false"]
        android:state_enabled=["true" | "false"]
        android:state_activated=["true" | "false"]
        android:state_window_focused=["true" | "false"] />
</selector>

 其他三个activity文件内容都一样，可以给各个activity用不同的布局，比如listView等：

public class AlbumsActivity extends Activity {
	public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        TextView textview = new TextView(this);
        textview.setText("This is the AlbumsActivity tab");
        setContentView(textview);
    }
}